Dwi2tensor_command


#1

Dear experts,
I am using the MRtrix to process diffusion kurtosis imaging with 7 b-values. When I run the dwi2tensor command, I got weird dkt image. The image cann’t shown properly in mrview with 14 volumes. Should I use dke image to conduct the following steps or use diffusion tensor image?
Thanks in advance!
Best,
Changhong


#2

Hi @Li_Changhong ,

Not sure what you’re referring to when you say the DKT image is “weird”. It’s definitely supposed to have that many volumes, which you can each see in mrview if you wish. We currently don’t implement any other commands yet that actually do something with the DKT image. The diffusion tensor image that goes with it though, is a valid DTI image that was fitted together with the DKT image; so the effects of the kurtosis have been taken into account in that fit.

Cheers,
Thijs


#3

Hi Thjis,
Would you be able to tell us how to use the output from
Dwi2tensor so we can calculate the Kurtosis, mean Kurtosis, kurtosis axial and radial diffusivities?
I am not sure how to do this from the output.

Thanks very much,
Nyoman

The tensor coefficients are stored in the output image as follows: volumes 0-5: D11, D22, D33, D12, D13, D23 ; If diffusion kurtosis is estimated using the -dkt option, these are stored as follows: volumes 0-2: W1111, W2222, W3333 ; volumes 3-8: W1112, W1113, W1222, W1333, W2223, W2333 ; volumes 9-11: W1122, W1133, W2233 ; volumes 12-14: W1123, W1223, W1233 ;


#4

Extracting kurtosis metrics from the DKT is (currently) not supported by tensor2metric.


#5

Hi @Nyoman_Kurniawan,

I’m not 100% sure about what your question exactly is:

  • If you’re asking if it can be done in a simple way with MRtrix, then the answer is “currently not”, as @bjeurissen said.

  • If you’re asking how to do it, then I suppose you’re probably asking about the definitions of those metrics, i.e., the mathematical formulas for MK, AK, RK and kurtosis anisotropy in function of the coefficients…? That has actually come up among ourselves recently, since we’ve been thinking about implementing them in tensor2metric. The challenge here, I reckon, is that there’s multiple (different) definitions out there… I’m not an expert myself in DKI metrics, but I remember coming across different definitions of some of the metrics. Any experts around on the forum that know if some definitions are considered more standard / accepted in the community?

Cheers,
Thijs


Preprocessing for AFD estimation
#6

@ThijsDhollander

Hi, sorry to resurrect an old topic, but I was wondering if there are any plans to implement diffusion kurtosis metrics in a future MRtrix version, given that it is increasingly seeming like an important technique? The definitions for these metrics may have become more standardised since 2016.

Here’s an article defining some metrics:

Qi, L., Han, D., & Wu, E. X. (2009). Principal invariants and inherent parameters of diffusion kurtosis tensors. Journal of Mathematical Analysis and Applications, 349(1), 165-180.